firestone



July 4 19h39- F. A. FIRESTQN; Re. 21,137

' onGAN original' Filed June 19. 1929` 3 Sheets-SM 2 ."-Efsx l'l): K l); l): ik l l ,C I l. 1U; 1U; s DE. R-,Gll

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LINVENToR FLOYD A. Fleas-TONE.

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\ 'y ATTORNEY July 4,1939.. F.A.F|REST9NE R@ 21,137

v cnam origipal Filed June 19,'1929 :s sheets-'sheet :s

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INVjNTGR y BY v ATTORNEY FLOYD A. FlRE'sToNE- Reissued July 4, 1.939

PA'rlazNT oFFlcE oaGAN moya A. Firestone,

corporation of illinois Ann Arbor, Mich., assignor to I Central Commercial Company l Chicagn IIL, a

original No. 1,953,153, ama April a, 1934-, serial No. 372,200, June 19, 19

Z9. Application fol' reissue March 9, 1936, Serial No. 07,991- v 57 Claims.

This invention relates to an improvement in' organs wherein the sound is produced by the generation of alternating currents of the proper frequency which currents are amplified and applied A Ato a loud speaker. 'Ihe objects of vthe improvements are to obtain an organ of greater tonal possibilities, more compact, and less expensive than the present compressed air organ.

The compressed air organ as usually built uses l() a separate set of pipes for each tone quality; thus,

there is a full scale ofpipes for imitating the clarinet tone, another for the trumpetjanother for the flute, etc. A complete organ consists of about six thousand pipes together with the necessary equipment for supplying compressed air .at different pressures. This equipment occupies a very large amount of space and costs $50,000 or more. Furthermore, its variety of tone qualities is limited by the inventiveness of the designers in producing pipes; many orchestral instruments have never been successfully imitated by the organ. My organ consists of one set of equip-1.`

ment which can by suitable.manipulation imitate the tone of any musical instrument; it is less expensive to construct than the compressed air organ and requires only as much space as a grand piano.

A musical tone consists of a fundamental tone and a number of harmonics. The pitch of the musical tone is determined by the number of vi* brations per second, commonly called the fref quency, constituting the fundamental tone. The harmonics have frequencies which are integral multiples of the fundamental frequency. Thus, if the fundamental frequency is 200 cycles per second, the second harmonic frequency will be 400, the third harmonic frequency 600, etc. The quality of a musical sound is that characteristic which enables us to distinguish the sound of the clarinet from'that of the violin, or the piano from the banjo. The quality is determined by the .intensity of the harmonics relative to the fundamental; by the rate at which theintensity of the fundamental and harmonics grows and decays at @harmonic of 'all the notes of theorgani- These the beginning and end of a note, commonly called true it. is also possible for me .to control A.the

relative phases of the variou/s component tones.

My device-contains a separate alternating current generatorV for each fundamental and each generators arelcontrolledby thelxeyson the keyboard of the console. (The console is that part' of an` organ which comprises the keyboards of the various manuals; the pedalkeyboard, if andthe necessary controls, ifvay, for regulating ,m the loudness 4and tonequality of thenctei 'prQ- duced.) 'The' currents are then amplified if necessary-with a vacuum tube amplifier whose amplification is continuously variable for controlling the loudness; the amplified currents are applied to a loud speaker capable of Converting electrical energy into acoustical energy.

Let us now consider what frequencies of altere hatingl current must beproducedv inv ,order to sound all'of the Cs on the organ including their Y, harmonics. There are on the organli Qs having the following frequencies lin cyclesperv second: 16, 32, 64, 128, 256, 512, 1024, '2048,` and,4096. The lowest of these would have va fundamental arid harmonics of the following frequencies: 16, 32,48, 64, 80, 96, 112, 128, 144etc. Some. of these harmonic frequencies are the saine. as the' fundamental frequencies of the otherCs, `Wlfiilesorrle are different. The note having a. 3,21 cycle fundamental has frequencies of 32,04, 964,411.2@ 1,60, etc. Some of these harmonic frequencies arel the same as those in the previous list for the v1 6 cycle fundamental. Thus, when one considersthe 9 vCys' and, say, 20` harmonics of each, leavingout those harmonics having frequencies higher than A4,096 cycles he finds that about different frequencies are required. For the C sharps, 60 more different frequencies must be produced. Since there are twelve notes in one octave the production of all the notes in the scale with their first twenty har'- l40 monies, leavingout the harmonics above 10,000 cycles would require '720 frequencies. It is obv vious that if the device is to be commercially prac.- ticabnle each generator must be extremely simple. Figs. 1a .and 1b illustrate theprincipleof 'a single alternating current generator, which principle may beused 4in applying my invention. Figs..

2a, 2b, and 2e show a practical combination of a large `number of valternating .current generators utilizing the above principle. Fig. 3 shows the 50 Ymethod. of driving a numberof similar groups of generators to produce all the frequencieaneeded in producing the notes o f the Vmusical scale. Fig. 4 gives the wiring diagram of a typical portion-of the complete organ, i

For purposes of sound production no distinction need be made between alternating current and direct current with alternating current superposed. A simple alternating current generator capable of producing sumcient voltage to actuate the grid circuit of a vacuum tube can be produced in many different ways, but the method which I prefer is shown in principle in Fig. '1b. A rotating metallic disc I on a shaft 2 is mounted in bearings 3 and 4 and driven by the synchronous motor 5 through the pulleys 6 and 1 and belt 8. Around the disc is a row of equally spaced holes 9. Twofstrips of metal I0 and II called inductors are mounted on insulating blocks I2 and I3 in such a manner that the holes 9 run close to them. If the switch I4 is closed on point I5 the battery I8 will charge the inductor I0. Owing to the electrostatic capacity between inductor I0 and inductor I I through the Vholes 9 the potential 'of the inductor,` II will always be greater when itis opposite a hole 9 than when it is opposite the grounded metallic disc I vbetween the holes 9.

Thusan alternating potential will be developed on the inductor II having the frequency with which holes 9 pass the 'inductor II. By properly shaping the inductor II and adjusting its distance from the holes 9 a pure wave free from harmonics can be obtained. The voltage thus generated may be taken to the conventional vac' uum tube amplifier I1 which isconnected to the 'loud speaker I8 through the potentiometer I9.

The rate at which the generator builds up its voltage when the switch I4 is closed is governed by the resistance 2I and the condenser 22. The inductor III does not arrive at the full voltage of the battery until the battery has charged the condenser 22 through the resistance 2|. It is well known that the time in seconds required to charge a condenser through a resistance is lroughly equal to the product of the capacity in farads and the lresistance in ohms.' Thus by adjusting the resistance 2| the generator may be made to build up its voltage instantly or gradually over a period of several seconds. To stop the generation of voltA age it is necessary to discharge inductor I0. This is done through the resistances 23 and 2I by whose regulation, the inductor I0 can be discharged instantly or gradually. Experiment has shown that if the inductor II! is charged to `200 volts the inductor II will deliver about 0.05 volts alternating current'to the amplifier I1, a value amplefor the operation of an amplier.

The final form of generator group shown in Figs. 2a, 2b and 2c is arrived at by the expansion of the principleof Fig. la by the use of three discs on one shaft, each disc having many rows of holes and each, row of .holes having one inductor on each side of and close to the disc. For simplicity each disc in Fig. 2a is drawn with only 6 rows of holes although in practice a larger number is'required as explained 'fully further on in this paragraph. 24, 25 and 26 are the three metallic discs which are fixed to the shaft 21. Shaft 21 is mounted in the bearings 28 and 29 and is driven by belt 30. 3 I, 32, and 33 are the insulated primaryv inductor groups to which the direct polarizing voltage is applied, there being a separate insulated metallic inductor plug for each row of holes. 34, 35, and 36 are the corresponding insulated secondary inductor groups from which the alternating currents are derived, there being a separate insulated metallic inductor plug for each row of holes. Arranged in any convenient manner on discs 24, 25, and 26 are concentric cir'- cular rows of holes, there being one each of rows having the following numbers of holes: 1, 2, i 5, 6, '7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 44, 48, 52, 56,

necessaryfor providing the harmonics of each of these fundamentals, all rows having more than 320 holes having been omitted as being of too I high a frequency.

If the generator group of Fig. 2c is driven'at 16.00 revolutions per second it is capable of producing all the frequencies necessary for all the Cs of the scale and all their necessary harmonics. An exactly similar generator group if driven at a speed of 16.95 revolutions per second is capable of producing all the frequencies vnecessary for all the C sharps of the scale and all their necessary harmonics. The frequencies of all `the notes of the musical scale and all their necessary harmonies can be produced by 1.2 similar generator groups running at the following speeds in revolutions per second: v16.00, 16.95, 17.96, 19.02, 20.15, 21.35, 22.62, 23.97, 25.39, 26.90, 28.50,4 and 30.19. The foregoing numbers are in the relation of the frequencies of the equitempered scale 'each being larger than the one just preceding by the twelfth root of 2. v

Fig. 3 shows schematically the entire generator assembly. The synchronous motor 31 drives the line shaft 38 through the belt 39. This line shaft drives the twelve generator groups 40 through the belts 4| each pulley 42 being of such size as to drive its generator group at one of the speeds listed above. In operation the metal parts of all generators are grounded. y

Fig. 4 shows a schematic diagram of the manner in which the generators are connected into the circuit so as to allow the musician to control them from the keyboard. 43 is the lowest C key on the keyboard; 44 is the next higher C key and 45 the next higher C above 44. These keys are provided with a multiplicity of contacts 45 arranged as -shown so that when the key is depressed the primary inductors of the generators 41 are connected to the polarizing battery 43 through the voltage` selecting switches 49 and the The symbol which has been chosen to represent these electrostatic generators in the diagram is that for acondenser with a numeral in thece'ntergl which indicates the'number of holes in th'e ro l of that particular generator. It will be lnoted fromthe drawings that the 1 hole generatif is controlled yby the fundamental contact on the lowest key, 43. The two hole generator ls controlled by the second harmonic contact on key 43 and also by the fundamental contact on key 44.r The connections are so arranged that if either key is depressed the primary inductor of the generator is disconnected from the grounding resistor 5I and connected to the appropriate polarizing voltage.

Similarly the 4 hole' generator is controlled by the fourth harmonic contact of key 43, by the d generator furnishes for the key which was de-v second harmonic contact'oi' key u, and bythe fundamental contact of key Il: Again if any of these keys is depressed the 4 hole generator is disconnected from the grounding resistor 5| and connected to the voltage, determined by the switches 4I, of that harmonic which the 4 hole Enough has beensaid to indicate the manner in which the C keys are connected with the C group of generators. 'Ihe C sharp keys and the C sharp group of generators form a set of connections separate from the C keys except that the C vsharp group derives its polarizing voltage from the same switches 4l and the secondary in-` ductors of the C sharp generator group are also connected to the input grid of the amplifier i1. Similarly for the other notes o! the scale. The secondary inductors of all the generators are permanently connected to the input grid of the amplifier I1 and thence through the potentiometer Il to the loud speaker il, but alternating voltage is supplied only by those generators whose primary lnductors are charged. If the generators are built for 20 harmonics of each notethen there will be 20 sets of contacts 48 on each key except those near the top'oithe scale, and 20 sets of re- 'slstors il and Il and condensers B2 for each key except those near the top of the scale. 'Ihere are, however,l only 20 switches Il for each manual of the organ as one switch regulates the voltage for all the fundamental frequencies, another' switch regulates the voltage for all the second harmonic frequencies, etc. By setting the switches Il the musician has absolute control of the steady state tone quality of the notes produced by the loud speaker il. The diil'erent manuals of the organ i use the same set of generators but each manual has a separate set of switches l! for controlling the relative intensity of the harmonics. Thus while the lowest note played on one manual might consist mainly of fundamental, this samepitch played on another manual might be very rich in there is only one generator of each of the reharmonics.

The purpose of condensers 52 in conjunction with resistors il and il is to regulate the attack, on the notes as was previously pointed out in the explanation oir Fig. lb.

It is obvious from the connections of Fig. 4 that if two keys are simultaneously depressed two voltages may at the same time be. applied 'to one of the primary inductors of a generator l1. In such case it 4is desirable that the resultant voltage should bes-approximately equal to the largest of the two. This result is achieved by placing resistors 53 in series with the voltage supply leads, the resistance in the higher volta'geleads being less than the resistance in the lower voltage leads.

In the above description of the method of connecting the generators it has been assumed that quired frequencies and that-each generator may serve as a harmonic of several notes. It is obvious, however, that several pairs of inductors might be disposed tangentially along a single row of holes andjthus serve as several separate generators `of the same frequency without an increase in the number of discs required. In some cases this might be of advantage in simplifying the connections as each harmonic would have its own generator and no generator would be required to serve more than one purpose.

If it should be found that the relative phase of the various harmonics inuences the tone quality,'then each pair of inductors on the generators may be arranged to move a short distance tangentially from its normal position, as shown in dotted lines in Fig. la, and in this way the relative phases of the generated currents can' be varied. l l

The ampliner may utilize as many stages as necessary and Ybe of sumcient power to supply the necessary volume without harmful distortion. The loud speaker may be of any sort of suitable device for converting electrical energy into acoustical energy although it is preferable that it should have a minimum amount of resonance so that the response may be lquick and free from frequency distortion. A good cone speaker, horn speaker, or Hewlett tone generator would be suitable. Its construction must be such as to allow it to handle the comparatively large energy. y

I have previously stated that by properly shaping the inductor Il (Fig. 1b) and adjusting its distance from the holes l a pure wave free from harmonics can be obtained. Such wave is expressed by a simple harmonic curve, and as it is perfectly simple, regularv and symmetrical it is called a sine curve. 'I'his premises, of course. a very accurate designing and proportioning of the holes 9 and Inductor Il as to relative shapes, dimensions and distance spacing. For practical purposes, however, it is not necessary that the wave produced be absolutely pure, i. e., truly sinusoidal, but only that it be substantially pure or substantially sinusoidal to suit the musical ear, since acoustically variations within a certain range fromA a pure tone will be found musically acceptable. If, for example, the inductor Il is shaped as shown ln Fig. 1a so that its width is equal to or but slightly exceeds the diameter of the holes 9 of predetermined circular design and diameter, a micrometric degree of spacing is unnecessaryv to obtain a wave form substantially free from harmonics, namely, a wave form, the harmonic content of which is less than 5%, the least amount of harmonic which the ear can detect and therefore representing a tone which is musically accepted as a pure tone and which is expressed by a simple harmonic curve.

. In Figures 2a, 2b and 2c, the holes in discs Il,

25 and 26 describe small circles. The inductors which are associated with said holes are cylin- 'produced by the variance of the capacitance between the two changes as a function of time and will be 4substantially of a sinusoidal wave' What I claim is:

1. In combination, means of generating alternating currents of a multiplicity of frequencies, a loud speaker, and means for regulating as a function of the time the amount of current of any-frequency supplied bysaidl generating means to said loud speaker.

2. In combination, a multiplicity of alternating current generators, a loud speaker, means for starting and stopping the delivery of alternating current from any aforesaid generator to said loud speaker, and means for regulating the rate of starting of the aforesaid delivery of alternating current. 3. In combination,v a multiplicity of alternating current generators, a loud speaker, means Vll) for starting and stopping the delivery of alternating current from any aforesaid generator to said loud speaker, means for regulating the rate of starting of the aforesaid delivery of alternating current, and means for regulating the rate of stopping of the aforesaid delivery of alternating current.

4. In combination, means ofgenerating alternating currents of a multiplicity of frequencies, a loud speaker, and means including a resistance and a capacity for regulating as a function of the time the amount of current of any frequency supplied from said generating means to said loud speaker.

51 In combination, means of generating currents of a multiplicity of frequencies, means for regulating as a function of the time the amount generated of alternating current of each fremanuals of keys;

quency, an amplifier, and a loud speaker.

6. In combination, means of generating alternating currents having the frequencies of the notes of the musical scale and their harmonics, means for regulating as a function of the time -theY amount generated of alternating current of each frequency, an amplifier, and a loud speaker.

'1. In combination, a multiplicity of alternating current generators, means for amplifying alternatingl currents, means for starting and stopping the delivery of alternating current yfrom any aforesaid generator to said amplifier,

means for regulating the rate of starting and the rate of stopping of the aforesaid delivery of alternating current, and means 'for'producing sounds from the amplified alternating currents. v

8. In combination, a multiplicity of alternat-` ing current generators, generating the frequencies of the notes of the musical scale and their harmonics, means for amplifying the alternating currents generated by said generators, Y

means for starting and stopping the delivery of alternating current from each aforesaid generator to said amplifier, means for regulating the rate of starting and the rate of stopping of the aforesaid delivery of alternating current, and a means-for producing sounds from `the amplified alternating currents.

9. In combination, a multiplicity of alternating current generators, a console, means for amplifying alternating currents, means controllable from said console for regulating as a function of the time the amount of alternating current delivered from any aforesaid generator to said amplifier, and means for producing sounds from the amplified alternating currents.

10. In combination, a multiplicity of alternating current generators generating the frequencies of the notes of the musical scale and their harmonics, a console, means for amplifying alternating currents, means controllable from said console for regulating as a function of the time the amount of alternating current delivered from any aforesaid generator tosaid amplifier, and means for producing sounds from the amplified alternating currents.

l1. In combination, a multiplicity of electrostatic alternating current generators each of which comprises a moving member, a primary inductor, and a secondary inductor, the mutual electrostatic capacity between said primary and secondary inductors being periodically varied by said moving member; a console ha'ving several separate means for each manual for controlling the charge on the primary inductor of any generator as a functioning .currents produced by said generators; and

means for producing sounds from the amplified' ators; and means for producing sounds from the of said generators; means for controlling the rate of charge and discharge of any of said primary inductors; means for amplifying the alternating currents generated by said generators: means for producing sounds from the amplied currents; and means for controlling the amount of alternating current delivered by said amplifler to said sound Vproducing means.

14. Inlcombination, a multiplicityv of electrostatic alternating current generators each of which comprises a moving member, a primary inductor, and a secondary inductor, the mutual electrostatic capacity between said primary and secondary inductors being varied periodically by said moving member; a console; means operable from said console for controlling the charge on' any of the primary inductors of said generators; means for amplifying the alternating cur-.,

rents generated by said generators; means for producing sounds from the amplied alternating currents; and kmeans for controlling the amount of alternating current delivered by said amplifier to said sound producing means.

l5. In combination, a multiplicity of electrostatic alternating current generators each of which comprises an insulated primary conducting plate, an insulated secondary conducting, plate; and a moving member so shaped and so placed as to periodically vary the mutual electrostatic capacity between said primary and secondary conducting plates; means for controlling the charge on the primary lconducting plate of any generator as a function of the time; and means for producing sounds from the voltages induced on the secondary conducting plates.

16. In combination, a multiplicity of electrostatic alternating current generators each of which comprises an insulated primary conducting plate, an insulated secondary conducting plate, and means for periodically varying the mutual electrostatic capacity between said primary and secondary conducting plates; means for controlling the charge on the primary conducting plate of any generator as a function of the time; and means for producing sounds from the voltages induced on the secondary conducting plates.

1'7. In combination, a multiplicity of electrostatic alternating current generators each of which comprises an insulated primary conducting plate, an insulated secondary conducting plate, and means for periodically varying the mutual electrostatic capacity between said primary "and secondary conducting plates; 'means for charging the primary conducting plate of any generator; Vmeans for utilizing part of the electrical energy induced on the secondary conducting plates.

18. In combination, Aan electrostatic alternating current generator` comprising conducting members insulated from each other, means for periodically varying the'mutual electrostatic capacity between said conducting members, means for charging an aforementioned conducting member, and means `for utilizing the voltage fluctuations of a conducting member. Y

19. In combination, a multiplicity of electrostatic alternating vgenerators comprising conducting members insulated from each other, means for periodically varying the mutual electrostatic capacity between said conducting members'. means. for controlling the charge on some aforementioned conducting members as a function of the time, an ampliner, and a loud speaker.A

20. In a musical instrument, an electrical sound producer, an electrical circuit for controlling the operation of said sound producer, a

multiplicity oi' capacity reactance assemblies, each of said capacity reactance assemblies comprising a pair of stator elements and an intermediate rotor element, and means for driving said rotor element for controlling the effective capacitive reactance of said electrical circuit at predetermined tone frequencies.

21. In' a musical instrument, an electrical sound producer, an electrical circuit for controlling the operation of said sound producer and a plurality of varying capacity assemblies, said varying capacity assemblies each comprising a pair of stator elements having aligned capacity areas, andan intermediate. rotary element apertured to alternately shield and Aexpose said capacity areas one with respect to the other, and connections between said varying capacity assemblies with said electrical circuit and controlling the capacitive reactance thereof and correspondingly controlling the tone frequencies produced by said'electrical sound producer.

22. In a system for the production of sound for musical expression, an electron tube system including an output circuit having an electrical sound producer connected therein for converting current impressed upon the circuit into audible sound; a source of potential; a plurality of continuously varying capacities providing different frequencies corresponding with the notes of a musical scale and interposed in the circuit between said source of potential and the input side of said output circuit; and means such as a key manual adapted to place vone or more of said continuously varying' capacities in circuit with said input side of the output circuit and including a system of key-actuated contacts for con- Aill -necting the capacities with and disconnecting same from said source of potential; and means actuable by the contacts for controlling as al function of time, the rate of growth and decay of tones corresponding to the notes of said musical scale. Y

23. In an electrical musical instrument; an. electrical sound producer;a an electrical circuit for controlling the operation of the sound producer; a multiplicity of capacity reactance assemblies, each comprising a pair of stator elements and an intermeidate rotor-element; and means -ior driving said rotor element for controlling the effective capacitive reactance of said electrical circuit at predetermined tone .frequencies; the stator elements providing aligned capacity areas, the rotor element being apertured to alternately/shield andexpose said capacity areas, and said stator elements being adjustable relative to theapertures of the rotor element to enable the phase relations of the frequencies produced by said multiplicity of assemblies to be "varied 24. In an electrical musicalinstrument, an amplifying circuit; a source of electrical' energy; groups of devices for producing electrical frequencies conforming to the frequencies of dinerent tones of a musicaiscale, each saidvdevice comprising` an inductor connected with the arnplifying circuit and a rotatable member spaced apart fromthe inductor and apertured to alternately shield and expose the inductor, so as to producean alternating voltage in the amplifying circuit of the frequency of a tone to be sounded;

means for driving the rotary element at a predetermined speed; and means by which the device can be connected with said source of energy to electricallyV charge the device.

v25. In an 'electrical musical instrument, an amplifying circuit; a source of electrical energy; and means for producing an alternating voltage of the .frequerpy of a.F musical tone and comprising an inductor connected with the amplifying circuit so thatv current delivered tothe inductor from said source can be impressed upon said circuit; a rotary element having apertures disposed relative to each other and to the inductor to alternately shield and expose same so that by rotation of said rotary` element, an alternating voltage conforming to the frequency of said musical tone can be impressed upon said circuit; and means for driving the rotary element at a predetermined, constant speed.

26. A device for originating any prescribed Wave-form, comprising Aa condenser and actuating means for continuously varying the capacitance of said condenser in accordance with said wave-form.

27. An electrical musical instrument for originating substantially sinusoidal waveforms translatable into sound, comprising a plurality of b condensers, and actuating means forcontinu- 'ously varying the capacitance of each'of said knating substantially sinusoidal waveforms translatable into sound, comprisinga plurality of condensers, and rotary actuating vmeans for varying the capacitance of each of said condensers by -relative motion at a substantially uniform rate between partsthereof; the design of each'of said condensers being such that the capacitances of said condensers vary substantially in accordance with sinusoidal waveforms and at harmonically related frequencies. Y

29. A device for originating a prescribed waveform of electric current, comprising aco'ndenser and actuating means for continuously varying the capacitance of said condenser in accordance with said waveform -by unidirectional relative motion between parts thereof ;A said capacitance being a periodic function of time analyzable into fml riodic function of time analyzable into a .constant component and a pluralityof'harmonically related sinusoidal components; said actuating means varying said capacitance by producing ro- 'tation of parts of said condenser relative to other parts thereof.

V31. A device for originating any prescribed waveform, comprising a condenser, an electrode in said condenser, an element in said condenser,

' and actuating means for movingA said element yms unidirectionally relative to said electrode, whereby the effective area of said electrode is continuously varied.

l32. In a device for originating a prescribed waveform of electric current, comprising a condenser, an electrode in said condenser, an element in said condenser, and actuating means for moving said element unidirectionally relative to said electrode, whereby the effective area of said electrode is continuously varied; saidcapacitance being a periodic function of time analyzable into a constant component and a. plurality of harmonically related sinusoidal components.

33. An electrical musical instrument for originating waveforms of electric current translatable into sound, comprising an electrical network, a plurality of condensers of variable capacitance, actuating means for continuously varying the capacitance of each of said condensers substantially in accordance with a sinusoidal Waveform by maintaining continuous unidirectional relative motion .between parts -of each of said condensers, and a plurality of means for selecting said condensers and for imposing their combined effects upon said network.

34. A device for originatinga prescribed Waveform, comprising an electric circuit, means for producing current variations in said circuit, and electrical means for selecting said rst means and for gradually varying its eiect upon said circuit.

35. A device for originating prescribed complex periodic waveforms of potential, .comprising a plurality of condensers, actuating means for vary-l ing the capacitance of eachy of said condensers by unidirectional relativeA motion between lparts thereof, means for selecting said condensers by establishing electric circuit connections thereto, and an electrical network wherein electric currents may be caused to flow by said condensers upon operation of the selecting means; Vthe capacitance Variation of each of said condensers being substantially sinusoidal; the frequencies of capacitance variation of the condensers of said plurality being substantially integral multiples of a common fundamental frequency, and said waveforms of `potential being produced by the synthesis of the potentials produced by individual condensers of said plurality upon operation of the selecting means. y

36. A device for originating prescribedwaveforms translatable into sound, comprising a plurality of groups of condensers, actuating means for varying the capacitances of said condensers in accordance with said waveforms by unidirectional relative motion between parts thereof, an electrical network, and electrical means for imposing'the effects of said condensers upon said network; said condensers and groups character- .of a group has a different ized by the fact that all the condensers of each y group have a common frequency of capacitance variation and by the fact that each condenser prescribed waveforr'n of capacitance variation.V

37. A device for originating a prescribed waveform, comprising an "electric circuit, a condenser of variable capacitance adapted to vary the negative reactance in said circuit, actuating means for continuously varying the capacitance of said` condenser in accordance with said waveform, a source of direct electromotive force for polarizing vsaid condenser, and electrical means for selecting said condenser and for gradually varying the effect of said condenser upon said circuit;

said electrical means comprising a pair of switch contacts and an impedance element for causing the magnitude of polarizing potential on said condenser to vary gradually following operation of said contacts.

38. A device for originating a prescribed wave- 'continuously' varying the capacitance `of said condenser in accordance with said waveform, a source of direct electromotive force for polarizing said condenser, and electrical means for selecting said condenser and for gradually varying the effect of said condenser on said circuit; said electrical means comprising a. pair of Vswitch contacts, and an impedance element for causing the magnitude lof polarizing potential on said condenser to approach a final value asymptotically following operation of said contacts.'

39. A device for originating prescribed waveforms, comprising an electric circuit', condensers of variable capacitance for varying the negative reactance in said circuit, actuating means for continuously varying the capacitancesof said condensers in accordance with said waveforms, a common source of direct electromotive force for polarizing said condensers, and electrical means for selecting each of saidcondensers and for gradually varying the effect of the selected condenser upon said circuit; said electrical means comprising at least two circuit branches; one of said branchesincluding a condenser and being such as to suppress sudden changes in potential drop across itself, and another of said branches including a. resistance elementand a switch and being such as to conduct direct current upon closure of said switch.

40. A device for originating a prescribed waveform translatable into sound. comprising an eleca source of direct electromotive force for charging said time-delay condenser through a resistance whereby the charging occurs gradually. and a circuit branch containing a resistance and adapted to be shunted around said second condenser, whereby said second condenser is gradually discharged and polarization is removed from said first condenser.

41. An electrical musical instrument adapted to originate prescribed complex waveforms of potential, said instrument comprising a plurality of condensers, actuating means for varying the capacitance of each of said condensers by unidirectional relative motion between parts there-l ot, means for selecting said condensers by establishing electric circuit connections thereto, and an electrical network wherein electric currents may be 'caused to flow by said condensers upon operation of the selecting means; the capacitance lvariation of each of said condensers being substantially sinusoidal; the frequencies of capacimeans for continuously varying the capacitances of said condensers in accordance with said -waveforms, a source of polarizing electro-motive force for said condensers, a coupling element havinga plurality of terminals. and means for selecting said condensers and for completing circuit branches 'between a treminal oi' said elementand a terminal of one of said condensers.

43. A device for originating a prescribed waveform,l comprising a condenser, actuating means for continuously varying the capacitance of said condenser in accordance with said waveform, a, vacuum-tube system, an input circuit i or supplying to the input terminals of said system an electromotive force translatable into sound, a source oi.' potential for polarizing said condenser;

anda coupling element for coupling said circuitv and said system; said circuit including said condenser, said source, and said element in series with one another.

44. A device for originating a prescribed waveform, comprising a circuit, a plurality of condensers of variable capacitance in said circuit for varying the negative reactance therein, and actuating means for continuously varying the capacitance of said condensers in accordance withv said waveform. a

45. A device for originating a prescribed waveform, comprising a circuit, a plurality of condensers, of variable capacitance, actuating means for continuously varying the capacitances 'of said condensers in accordance with prescribed waveforms, and means for selecting said condensers and for imposing their combined eiect upon said circuit to produce said first waveform.

46. A device for originating `a prescribed Waveiorm, comprising a circuit, a condenser of variable capacitance in said circuit for varying the negative reactance therein, actuating means for continuously varying the capacitance of said condenser in accordance with said waveform, and an electrical amplier connected to said circuit.

47. A device for originating a prescribed waveform comprising a circuit, a condenser of variable capacitance in said circuit for varying the .negative reactance therein, actuating means for continuously varying the capacitance of said condenser in accordance with said waveform, anI electrical amplier connected to said circuit, and

a sound translating device connected to said amplifier.

48. A device for originating a prescribed waveform, comprising aclrcuit, a condenser of variable capacitance adapted to vary the negative reactance in said circuit, actuating means for continuously varying thev'eapacitance of said condenser in accordance with said waveform, and

electrical means for selecting said condenser and for Vgradually varying the eect of said condenser e lupon said circuit.

49'. A device for originating waveforms transingthe negative reactance in said circuit and for producing in said circuit potentials translatable into sound, actuatingv means for varying the capacitances of said condensers, a common source of direct electromotive force for polarizing said condensers',"and electrical means for selecting each oi said condensers and for gradually varying the effect ofthe selectedcondenser upon said circuit; said electrical means comprising at least two branches; one of said branches including a ltime-delay` condenser and being such as to suppress sudden changes of potential drop across itself. and another of said branches including a resistance element, a pair of contacts, and a control switch adapted to coact with said contacts.

50. In an electrical instrument an electrical network having therein a plurality of means for producing frequency variations of current, a plurality of groups ot selectors, and a frequency-selective control for regulating the relative eurrent intensities foreach of said groups.

51. In combination, a multiplicity of sources of alternating current, means for amplifying the alternating currents delivered from said sources,

means for starting and stopping the delivery ot alternating current from any one of said sources to saidvamplifying means, means for regulating the rate of starting and the rate of Skipping of the aforesaid delivery of alternating current, and means controllable from a console for determining which of said sources shall deliver alternating current to said amplifying means and for predetermining the intensity of said current.

52. In kan electrical musical instrument, a manualv including a number of diiferent keys, a set of switches'operated by each key, a plurality of` sources of alternating current, an electrical network in which switches of diiferent sets are connected with a single one of said sources, an amplifier in said network, means actuable from a console for determining which of said `sources shall be eilectivein-the network to conduct alv latableinto sound, comprising `an electric cir cuit, condensers of variable capacitance for varysion oi' said keys and for determining the intensity of said current, a sound producer actuable by said amplier, and means for controlling the amount of alternating current delivered by said amplifier to said sound producer.

53. In an electrical musical instrument, a.

manual including a number of diierent keys, a

set of switches operated by each key, a.` source of alternating current, electrical connections between said source and' several switches, each of a. diierent set, a plurality of additional. sources of alternating current of different frequencies, elec- A trical connectionsbetween said additional sources and other switches of said sets of switches, and means for regulating as a function of time the amount of alternating current conducted to an amplifier from any of said sources.

54. In an electrical musical instrument, ai

manual including a number of keys, a set of switches operated byveach key, a plurality of sources of alternating-current of different tone frequencies, electrical connections between each of said sources and different switches of aV plurality of said sets of switches, and means for gradually varying the effect of any source upon an electrical network upon depression of a key.

55. In an electrical musical instrument, the

combination of a plurality of sources of alternating current, each of a different tone frequency,

Va conductor common to said sources, lszey condelivered to said conductor from preselected ones of said sources, and means for regulating as a function of time the rate 'at which the intensity of tones grows and -decays of the translating means.

56. In an electrical musical instrument, mechanism for altering the tone quality of the nstrument comprising a plurality of manually actuable circuit controllingv devices for determining the number and relative intensities of harmonically related tone frequencies required for the production of a desired quality of tone,

each o'f said devices adapted for independent actuation to a number of different positions corresponding todifferent degrees of intensity of a Y'particular harmonic or fundamental and means for regulating as a function of time the rate at which the intensity of tones produced by the instrument grows and decays.

57. An electrical v musical instrument comprising a plurality of alternating current sources for originating alternating currents ofl different tone frequencies, means enabling a plurality of said sources to be used for the production of a complex tone, and means for varying 'the phase relation of said alternating currents,

FLOYD A. FIRESTONE. 

